In a four-stroke engine cycle there is the intake, compression, power, and exhaust. Each stroke corresponds to one full action of the piston. In a four-stroke cycle, or "Otto Cycle," two revolutions of the crankshaft are required to complete the process. In a two-stroke engine the cycle is completed within two piston strokes. Usually a two-stroke engine is usually more powerful than a four-stroke engine of equal size. However the drawback of a two-stroke engine is the amount of inefficient exhaust and pollution created from the unspent fuel that tends to leak through.
Heat Engines may also fall under the category of Internal Combustion engines. The first experiments of internal combustion engines were experimented by a Dutch scientist named Christian Huygens way back in 1680 A.D. Real headway was not made until almost two centuries later when around 1876, the right technology and brains were united and sustainable internal combustion motors were born and commercialized.
It not uncommon to hear conflicting advice on what type of oil should be used in a motorcycle engine. Manufacturers usually advise using synthetic, man-made oil, which has longer-lasting properties compared to natural oil. Indeed it will not wear as quickly and natural oil can retain viscosity easier. One thing is for certain, oil is still cheap enough to burn.
Automobile car oil is efficient in a motorcycle engine as well. Assuming it is proper viscosity and the motorcycle engine is well maintained. No matter which kind of oil is put into a motorcycle engine, the motorcycle is going to break it down much faster than a car would.
Most kinds of oil come with a rating of 20W-50 that tells you that it can maintain integrity at low and high temperatures. Heat will rapidly break down oil; a low rating would indicate the oil is unsuitable for elevated engine temperature. Synthetic oil has long-lasting polymer chains that resist breakdown better than natural oil polymers in elevated temperatures.
Some times a specific model of motorcycle will have a commonly diagnosed problem with its engine. Particularly the older motorcycles, such as the Kawasaki EX500 (which tends to pop out of gear when the brake is applied), retain problems characteristic to their engines.
If you are shopping for a used motorcycle one of the most important components you should check first is the engine. The seller may have warmed up the engine prior to you testing it, which would hide any problems it may have starting when cold. Therefore request that the seller not warm up the engine before you get there. You can see if the motorcycle engine cases are warm but be careful because they can get quite hot. There will be traces of heat for a few hours after an engine has been warmed. If you do detect traces of warmth, elect to explore other parts of the motorcycle while the engine cools. It's especially important to check the starting capabilities of a kick-start motorcycle engine while it's cold.
The sound of an unhealthy motorcycle engine is clacking or like that of gravel in a can. If there is a lot of hesitation or faltering as the engine starts, it could be issues with the carburetor. Unless you have a fuel-injected motorcycle in which case the problem may be much more complicated.
Issues with cable routing can be easily detected by fully turning the handle bars left and right while the bike is running on neutral. If the engine revs without you twisting the throttle, or twisting just a tiny bit, then there is a problem with how the motorcycle cables are routed.
When the engine has been off for a few minutes and the motorcycle is on even ground you can check the oil level. There should be a viewing glass or dip-stick on the right side of the motorcycle engine. The optimum oil level is between the upper lower edges of the glass or between the upper and lower ridges on the dip-stick. Too low is just as bad as the oil being too high. It is definitely a bad sign if you ask the owner when was the last time the oil was changed and he or she doesn't know. Every six months, or 5,000 miles, is a good rule of thumb for changing motorcycle oil. Also, make sure there's a fresh batch of oil in the engine right before the bike is stored during the winter.
What does the color of the oil mean?
Golden color: The oil has been changed very recently (fades to black with more use and time)
Black: The motorcycle oil is old-find out when it was last changed.
White Streaks: Water has gotten into the oil from condensation or worse, a leak in the coolant system. After 20-30 minutes of the engine running, the white streaks may be burned off. If this is the case then it was probably just condensation and there's nothing wrong. Otherwise major engine work is required.
Grey oil: Contains aluminum particles, which is alright for a dirt bike but dangerous in a street bike.
Shiny Flecks of Metal: Major disintegration of motorcycle engine. Sign of heavy wear.
Check coolant level to make sure it's not too high or low. The color of the motorcycle coolant should be a bright green, not murky or clear. Once that is taken care of you can have a mechanic do a compression test on the engine. It's not highly important to have done, unless there is blue smoke coming out of a hot motorcycle engine in which case you can look for another bike or take it to a professional.
Used motorcycles can be risky to purchase, especially if you don't know what to look for. By being diligent in research and quizzing the seller, you can get a good deal and feel secure with your own motorcycle.
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